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991.
F. Carrasco D. Sánchez I. Vadillo B. Andreo C. Martínez L. Fernández 《Environmental Geology》2008,54(3):575-585
The water framework directive (WFD) is applied within the Guadalhorce river basin, a Western Mediterranean basin in the Málaga
province (South Spain). Criteria defining different surface and groundwater bodies are described. The basic hydrographic network
is constituted of low-mountain and low-altitude Mediterranean mineralized rivers. Heavily modified surface water bodies correspond
(1) to areas where dams regulate the main watercourses, (2) to areas downstream of reservoirs, where river flow is reduced,
and (3) to the coastal sector of the river where artificial channelling has caused morphological variations. Groundwater bodies
are related to carbonate and porous aquifers and, locally, to aquifers influenced by dissolution of evaporites. The main impacts
to water bodies are irrigated lands and livestock farming. There are also point sources of pollution, such as wastewater,
landfills, golf courses, industrial zones, quarries and petrol stations. In addition, groundwater is frequently pumped for
human supply and irrigation. Qualitative status of groundwater bodies was done by chemical analysis of samples from a monitoring
network and the quantitative status by examining variations in piezometric levels. Both revealed the existence of water bodies
at risk of not meeting the environmental objectives of the WFD. The main indicators of pollution are nitrates related to agricultural
activities, and total organic carbon (TOC), PO43− and NH4+ in relation to wastewater. 相似文献
992.
María Yanina Esper Angillieri 《Environmental Geology》2008,55(1):107-111
This work analyzes various morphometric characteristics of the Colangüil river basin in order to evaluate flash flood hazards.
Such high-water events pose a risk to the similarly named small village located at the basin’s foot area. For this purpose,
the basin is divided into seven sub-basins and some basic measurements (surface, perimeter, basin length, river beds, elevations
and slope of the main river bed, and of a number of minor river beds) are calculated. These measurements permit to predict
approximately the behavior of the basin in the presence of a series of theoretical rainstorms that may generate unusual runoff
volumes that make up such flash floods. 相似文献
993.
Xiomara Cazañas Pura Alfonso Joan Carles Melgarejo Joaquín Antonio Proenza Anthony Edward Fallick 《Mineralium Deposita》2008,43(7):805-824
The El Cobre deposit is located in eastern Cuba within the volcanosedimentary sequence of the Sierra Maestra Paleogene arc.
The deposit is hosted by tholeiitic basalts, andesites and tuffs and comprises thick stratiform barite and anhydrite bodies,
three stratabound disseminated up to massive sulphide bodies produced by silicification and sulphidation of limestones or
sulphates, an anhydrite stockwork and a siliceous stockwork, grading downwards to quartz veins. Sulphides are mainly pyrite,
chalcopyrite and sphalerite; gold occurs in the stratabound ores. Fluid inclusions measured in sphalerite, quartz, anhydrite
and calcite show salinities between 2.3 and 5.7 wt% NaCl eq. and homogenisation temperatures between 177 and 300°C. Sulphides
from the stratabound mineralisation display δ
34S values of 0‰ to +6.0‰, whilst those from the feeder zone lie between −1.4‰ and +7.3‰. Sulphides show an intra-grain sulphur
isotope zonation of about 2‰; usually, δ
34S values increase towards the rims. Sulphate sulphur has δ
34S in the range of +17‰ to +21‰, except two samples with values of +5.9‰ and +7.7‰. Sulphur isotope data indicate that the
thermochemical reduction of sulphate from a hydrothermal fluid of seawater origin was the main source of sulphide sulphur
and that most of the sulphates precipitated by heating of seawater. The structure of the deposit, mineralogy, fluid inclusion
and isotope data suggest that the deposit formed from seawater-derived fluids with probably minor supply of magmatic fluids. 相似文献
994.
Michael Schnabel Dieter Franke Martin Engels Karl Hinz Snke Neben Volkmar Damm Stefan Grassmann Hugo Pelliza Paulo Ricardo Dos Santos 《Tectonophysics》2008,454(1-4):14-22
It is well established that the Argentine passive margin is of the rifted volcanic margin type. This classification is based primarily on the presence of a buried volcanic wedge beneath the continental slope, manifested by seismic data as a seaward dipping reflector sequence (SDRS). Here, we investigate the deep structure of the Argentine volcanic margin at 44°S over 200 km from the shelf to the deep oceanic Argentine Basin. We use wide-angle reflection/refraction seismic data to perform a joint travel time inversion for refracted and reflected travel times. The resulting P-wave velocity-depth model confirms the typical volcanic margin structure. An underplated body is resolved as distinctive high seismic velocity (vp up to 7.5 km/s) feature in the lower crust in the prolongation of a seaward dipping reflector sequence. A remarkable result is that a second, isolated body of high seismic velocity (vp up to 7.3 km/s) exists landward of the first high-velocity feature. The centres of both bodies are 60 km apart. The high-velocity lower-crustal bodies likely were emplaced during transient magmatic–volcanic events accompanying the late rifting and initial drifting stages. The lateral variability of the lower crust may be an expression of a multiple rifting process in the sense that the South Atlantic rift evolved by instantaneous breakup of longer continental margin segments. These segments are confined by transfer zones that acted as rift propagation barriers. A lower-crustal reflector was detected at 3 to 5 km above the modern Moho and probably represents the lower boundary of stretched continental crust. With this finding we suggest that the continent–ocean boundary is situated 70 km more seaward than in previous interpretations. 相似文献
995.
Variations in the accuracy of gravity recovery due to ground track variability: GRACE,CHAMP, and GOCE 总被引:4,自引:2,他引:2
J. Klokočník C. A. Wagner J. Kostelecký A. Bezděk P. Novák D. McAdoo 《Journal of Geodesy》2008,82(12):917-927
Following an earlier recognition of degraded monthly geopotential recovery from GRACE (Gravity Recovery And Climate Experiment)
due to prolonged passage through a short repeat (low order resonant) orbit, we extend these insights also to CHAMP (CHAllenging
Minisatellite Payload) and GOCE (Gravity field and steady state Ocean Circulation Explorer). We show wide track-density variations
over time for these orbits in both latitude and longitude, and estimate that geopotential recovery will be as widely affected
as well within all these regimes, with lesser track density leading to poorer recoveries. We then use recent models of atmospheric
density to estimate the future orbit of GRACE and warn of degraded performance as other low order resonances are encountered
in GRACE’s free fall. Finally implications for the GOCE orbit are discussed. 相似文献
996.
The fixed gravimetric boundary-value problem (FGBVP) represents an exterior oblique derivative problem for the Laplace equation. Terrestrial gravimetric measurements located by precise satellite positioning yield oblique derivative boundary conditions in the form of surface gravity disturbances. In this paper, we discuss the boundary element method (BEM) applied to the linearized FGBVP. In spite of previous BEM approaches in geodesy, we use the so-called direct BEM formulation, where a weak formulation is derived through the method of weighted residuals. The collocation technique with linear basis functions is applied for deriving the linear system of equations from the arising boundary integral equations. The nonstationary iterative biconjugate gradient stabilized method is used to solve the large-scale linear system of equations. The standard MPI (message passing interface) subroutines are implemented in order to perform parallel computations. The proposed approach gives a numerical solution at collocation points directly on the Earth’s surface (on a fixed boundary). Numerical experiments deal with (i) global gravity field modelling using synthetic data (surface gravity disturbances generated from a global geopotential model (GGM)) (ii) local gravity field modelling in Slovakia using observed gravity data. In order to extend computations, the memory requirements are reduced using elimination of the far-zone effects by incorporating GGM or a coarse global numerical solution obtained by BEM. Statistical characteristics of residuals between numerical solutions and GGM confirm the reliability of the approach and indicate accuracy of numerical solutions for the global models. A local refinement in Slovakia results in a local (national) quasigeoid model, which when compared with GPS-levelling data, does not make a large improvement on existing remove-restore-based models. 相似文献
997.
A new method for three-carrier GNSS ambiguity resolution 总被引:2,自引:2,他引:0
U. Fernández-Plazaola T. M. Martín-Guerrero J. T. Entrambasaguas 《Journal of Geodesy》2008,82(4-5):269-278
A new method for resolving the carrier-phase integer ambiguity in Global Navigation Satellite Systems (GNSS) is presented:
the MOdified Cholesky factorization for Ambiguity (MOCA) resolution. The characteristics and features of this method are described
and results obtained using a software simulator and an emulator are presented to validate its efficiency. The results are
then compared to those obtained using another existing method and good performance of the MOCA method in new GNSS systems
is shown. Furthermore, the proposed method yields accurate results even when short time spans are used or when there are poor
estimations of measurement error, making it immune to non-ideal conditions and ultimately a practical solution for real applications. 相似文献
998.
Sergio Mejía 《The Cartographic journal》2017,54(2):163-172
The first attempted republican map of present-day Colombia remained unachieved. Francisco José de Caldas worked on it since 1797 and, come the revolution and Nueva Granada's republican inception, he prepared two successive cartouches to introduce it: the first one in 1811, the latter in 1815. Finally entitled Provincias de la Nueva Granada, Caldas's map remains understudied. In this article, I establish its basic cartographic parameters, discuss the political context of its unfinished making and link it to its pertinent cartographic precedents. 相似文献
999.
Remote leveling of tide gauges using GNSS reflectometry: case study at Spring Bay,Australia 总被引:1,自引:1,他引:0
We further developed a new approach using GNSS reflectometry to determine the leveling connection between a tide gauge and a GNSS antenna. This approach includes the optimization of the unknown receiver bandwidth and the estimation of frequency changes in the signal-to-noise ratio (SNR) oscillation through an extended Kalman filter/smoother algorithm. We also corrected the geometric bending of the GNSS signals due to tropospheric refraction using local meteorological observations. Using 3 weeks of SNR data in Spring Bay, Australia, from a GNSS antenna placed sideways (i.e., ground plane orientated vertically and directed in azimuth toward the sea surface) to improve the SNR interference near the horizon, we obtained mean leveling differences of approximately 5 mm, with an RMS of approximately 3 cm level with respect to the nominal leveling from classical surveying techniques. SNR data from three different receiver manufacturers, coupled to the same antenna, provided similar leveling results. With a second antenna in the usual upright configuration, we obtained mean leveling differences of 1–2 cm and a RMS of about 10 cm. In the upright configuration, the leveling differences may include errors in the GNSS antenna phase center calibration, which are avoided in our technique but not in the classical surveying techniques. These results demonstrate the usefulness of the reflectometry technique to obtain precisely and remotely the leveling between a GNSS antenna and a tide gauge. In addition, this technique can be applied continuously, providing an independent and economical means to monitor the stability of the tide gauge zero. 相似文献
1000.
Francisco?J.?MoralEmail author Elena?Pulido Antonio?Ruíz Fernando?López 《Theoretical and Applied Climatology》2017,129(3-4):881-889
The present work reports on a methodology to assess the climatic severity of a particular geographic region as compared to specific information available in the current regulations. The viability for each of the 387 municipalities in the Autonomous Community of Extremadura (Spain) is analysed, making a distinction between those with reliable climate reports and those for which no such information is available. In the case study, although the weather conditions in Extremadura are quite homogeneous according to the Spanish Technical Building Code (STBC 2015) classification and most areas are associated to zone C4 (soft winters and hot summers), the southern area in the region is associated to zone D1, similar to the north of Spain, where winters and summers are cool, which does not coincide with the actual climate in the south of Extremadura. The general climatic homogeneity in Extremadura was also highlighted with the new procedure, predominating zone C4, but unexpected or unreal climatic zoning was not generated, giving place to a consistent spatial distribution of zones throughout the region. Consequently, the proposed method allows a more accurate climatic zoning of any region in agreement with the Spanish legislation on energy efficiency in buildings, which would enhance the setting of thermal demand rates according to the actual climatic characterisation of the area in which a particular municipality is located. 相似文献